Calcium Accumulation and Neuronal Damage in the Rat Hippocampus following Cerebral Ischemia

The present study was undertaken to correlate calcium accumulation with the development of neuronal necrosis following transient ischemia. After 10 min of forebrain ischemia in the rat--a period that leads to reproducible damage of CA1 pyramidal cells--determination of calcium concentration and evaluation of morphological signs of cell body necrosis in the dorsal hippocampus were performed at various recirculation times. Tissue calcium concentration was not different from control at the end of ischemic period and did not change after 3, 6, 12, or 24 h of recirculation. However, after 48 h, calcium content increased significantly, with a further increase being seen after 72 h. At early recovery periods, only scattered necrotic neurons were observed. After 48 h, only 2 of 12 hemispheres showed more than 25 necrotic cells per section. More conspicuous neuronal death was observed after 72 h. The results thus demonstrate that net accumulation of calcium in regio superior of the hippocampus precedes marked necrosis of CA1 pyramidal cells. The results suggest that one primary event in the delayed death of these cells is membrane dysfunction with increased calcium cycling.